On Mon, Oct 09, 2023 at 05:09:28PM -0700, Roman Gushchin wrote: > Switch to a scope-based protection of the objcg pointer on slab/kmem > allocation paths. Instead of using the get_() semantics in the > pre-allocation hook and put the reference afterwards, let's rely > on the fact that objcg is pinned by the scope. > > It's possible because: > 1) if the objcg is received from the current task struct, the task is > keeping a reference to the objcg. > 2) if the objcg is received from an active memcg (remote charging), > the memcg is pinned by the scope and has a reference to the > corresponding objcg. > > Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@xxxxxxxxx> Other than one nit below: Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx> > --- > include/linux/memcontrol.h | 6 +++++ > mm/memcontrol.c | 47 ++++++++++++++++++++++++++++++++++++-- > mm/slab.h | 10 +++----- > 3 files changed, 54 insertions(+), 9 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 277690af383d..0e53b890f063 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -1769,6 +1769,12 @@ bool mem_cgroup_kmem_disabled(void); > int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order); > void __memcg_kmem_uncharge_page(struct page *page, int order); > > +/* > + * The returned objcg pointer is safe to use without additional > + * protection within a scope, refer to the implementation for the > + * additional details. > + */ Let's add the definition of scope in the above comment as well like set_active_memcg and slab memcg hooks.
